Stator for starter motor

ABSTRACT

In a stator, which is composed of a stacked core, for a starter motor according to the present invention, the stacked core being arranged such that a plurality of sheet members each having a yoke portion and a pole portion are disposed like a band, adjacent sheet members are stacked and coupled with each other so that the ends of the yoke portions thereof are overlapped, the plurality of sheet members are made to an annular shape by being bent at the coupled portions thereof to cause the pole portions to face the center of the annular shape, and the plurality of sheet members are formed in at least an approximately linear shape when developed, resin winding cores are interposed between the pole potions and wires wound around the pole portions. With this arrangement, there can be obtained a stator for a starter motor the cost of which can be reduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a stator for a starter motor used invehicles and the like, and more particularly, to a stator for a startermotor having a bendable stacked core.

2. Description of the Related Art

FIG. 14 is a perspective view showing the structure of a stator for aconventional starter motor; FIG. 15 is a plan view of the stator; andFIG. 16 is a perspective view showing an assembly process of the stator.

In the figures, four poles 104 are disposed in a cylindrical yoke 103.Field coils 107 are mounted on the four poles 104.

In the conventional stator arranged as described above, the yoke 103 isarranged as the cylindrical yoke (“bent yoke portion”) by rounding asheet member and welding the joints thereof. Spigot portions 106, whichare formed at the ends of the yoke 103 in the axial direction thereof,are processed by machining, and fitted to not shown brackets.

Further, the poles 104 are made in a different process by, for example,forging or the like and mounted on the yoke 103 later. Furthermore, thefield coils 107 are previously wounded in a different process and thespaces between wires are previously subjected to insulation processingby powder coating or the like.

The conventional stator arranged as described above is assembled in sucha manner that, first, the electric field coils 107, which have beenwounded and subjected to the insulation processing, are mounted on thepoles 104. Then, the poles 104 are mounted on the yoke 103 through themounting holes 103 a thereof by caulking, screws or the like.

In the stator for the starter motor arranged as described above, theyoke 103 must have a predetermined thickness because a yoke made of athin sheet member cannot achieve its function. Thus, the yoke 103 ismade in such a manner that a thick sheet member is cut off by a largepress and gradually rounded so as to be formed in a cylindrical shape,then the cylindrical thick sheet member is subjected to a drawingprocess to provide it with accuracy by making the deformed portions ofthe cylindrical member to a perfect cylindrical shape. Thereafter, thespigot portions 106 are machined at the ends of the cylindrical memberin the axial direction thereof and the mounting holes 103 a are drilledto the cylindrical member.

The conventional so-called “bent yoke portion” made by the above methodrequires many dedicated apparatuses such as a large press, welder,outside diameter drawing machine, lathe, drilling machine, coatingmachine, and the like. Further, many processes are necessary tomanufacture the “bent yoke” and the respective processing apparatusesare large in size, from which a problem arises in the manufacture of the“bent yoke”.

SUMMARY OF THE INVENTION

An object of the present invention, which was made to solve the aboveproblems, is to provide a stator for a starter motor whose manufacturingcost can be reduced.

In the stator, which is composed of a stacked core, for the startermotor according to the present invention, the stacked core beingarranged such that a plurality of sheet members each having a yokeportion and a pole portion are disposed like a band, adjacent sheetmembers are stacked and coupled with each other so that the ends of theyoke portions thereof are overlapped, the plurality of sheet members aremade to an annular shape by being bent at the coupled portions thereofto cause the pole portions to face the center of the annular shape, andthe plurality of sheet members are formed in at least an approximatelylinear shape when developed, resin winding cores are interposed betweenthe pole potions and wires wound around the pole portions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall perspective view showing a stator for a startermotor of an embodiment 1 of the invention;

FIG. 2 is a plan view showing how a stator core is made by stacking thinsheets circularly;

FIG. 3 is a plan view showing how a stator core is made by stacking thinsheets linearly;

FIG. 4 is a plan view showing how a resin winding frame is formed aroundpole portions;

FIG. 5 is a plan view showing how a magnetic field wire is wound aroundthe winding frame;

FIGS. 6 is a plan view showing how a stator core is rounded in acylindrical shape and the joint portions thereof are welded;

FIG. 7 is an overall perspective view showing the stator for the startermotor of an embodiment 2 of the invention;

FIG. 8 is a perspective view showing a manufacturing process of thestator of the embodiment 2 of the invention;

FIG. 9 is an overall perspective view showing the stator for the startermotor of an embodiment 3 of the invention;

FIG. 10 is an overall perspective view showing the stator for thestarter motor of an embodiment 4 of the invention;

FIG. 11 is an overall perspective view showing the stator for thestarter motor of an embodiment 5 of the invention;

FIG. 12 is a perspective view showing a manufacturing process of thestator of the embodiment 5 of the invention;

FIG. 13 is a sectional view of the starter motor of the embodiment 5 ofthe invention;

FIG. 14 is a perspective view showing the structure of a stator for aconventional starter motor;

FIG. 15 is a plan view of the conventional stator; and

FIG. 16 is a perspective view showing an assembly process of theconventional stator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1 is an overall perspective view showing a stator for a startermotor of a first embodiment of the invention. FIGS. 2 to 6 are planviews showing manufacturing processes of the stator, respectively,wherein FIG. 2 is a plan view showing how a stator core is made bystacking thin sheet members circularly; FIG. 3 is a plan view showinghow the stator core is made by stacking the thin sheet members linearly;FIG. 4 is a plan view showing how winding frames of resin are formedaround pole portions; FIG. 5 is a plan view showing how a field windingsare wound around the winding frames; and FIG. 6 is a plan view showinghow a stator core is rounded in a cylindrical shape and the jointsthereof are welded.

A stator core 1 of the first embodiment is generally called a “bentcore” which is made by stacking thin sheet members such as silicon steelsheets or the like which have been stamped and caulked by a press, asshown in, for example, Japanese Unexamined Patent ApplicationPublication No. 2000-116075. In the stator core 1, yoke portions 3 arearranged integrally with pole portions 4.

That is, a plurality of sheet members each having a yoke portion 3 and apole portion 4 are disposed like a band and stacked and coupled witheach other so that the ends of the yoke portions 3 of adjacent sheetmembers are overlapped. The sheet members each having a convex portionon one surface and a concave portion on the other surface aresequentially overlapped with each other at coupling portions 2 andstacked. As a result, the sheet members can be bent at the couplingportions 2, which permits the sheet members to be formed in an annularshape by being bent at the coupling portions 2 with the pole portions 4facing the center of the annular shape. In contrast, when the annularsheet members are developed, they can be bent to cause the pole portions4 to be disposed externally radially so that a wire can be easily woundaround the pole portions 4.

A manufacturing method of the stator core will be described withreference to FIGS. 2 to 6.

In FIG. 2, the yoke portions 3 are formed integrally with the poleportions 4 and stacked by being stamped and caulked as described above.At the time, the respective yoke portions 3 are coupled with each otherthrough the coupling portions 2 so that they can be developed at leastlinearly as shown in FIG. 3. The yoke portions 3 can be turned about thecoupling portions 2, respectively. It should be noted that when thesheet members are stacked, they may be disposed circularly as shown inFIG. 2 or may be disposed linearly as shown in FIG. 3.

After the sheet members are stacked as described above, winding frames 5made of resin are formed around the pole portions 4 by a resin moldingmethod as shown in FIG. 4. At this time, spigot portions 6, which arefitted to not shown brackets, are formed at the ends of the windingframes 5 in the axial direction thereof together with winding frames 5.The spigot portions 6 are stepped portions formed around the entirecircumference of the winding frames 5.

Thereafter, field windings 7 are wound round the winding frames 5 formedaround the pole portions 4 in a process shown in FIG. 5. After the fieldwindings 7 are wound, the stator core 1 is rounded in a cylindricalshape in a process shown in FIG. 6, and the abutting sections at boththe ends thereof acting as joint portions are welded by laser welding orthe like.

In the stator for the starter motor of the first embodiment arranged asdescribed above, the stator core 1 can be formed in at least anapproximately linear shape when it is developed, and the field windings7 can be directly wound around the pole portions 4 because the windingframes 5 are formed around the pole portions 4. The insulating propertyof the wound wires can be improved without damaging the insulating filmsthereof because the winding frames 5 prevent the magnetic field wire 7from being in direct contact with the pole portions 4. Further, it isalso possible to wind wires having no insulating film while sandwichinginter-wire members (for example, insulating papers) or the like betweenthe wound wires.

Further, the manufacture of the stator core 1 does not require largeprocessing apparatuses because it is arranged as the stacked core andcan be made by simple apparatuses such as a general-purpose press,molding machine, winder and the like, whereby the manufacturing cost ofthe stator core 1 can be reduced.

Further, in the first embodiment, the spigot portions 6, which arefitted to the not shown brackets, are formed at the ends of the windingframes 5 in the axial direction thereof. The formation of the spigotportions 6 simultaneously with the formation of the winding frames 5 bymeans of by the resin molding method eliminates the need of conventionalmachining, which can reduce the manufacturing cost of the stator core 1.

Note that, in the first embodiment, the field windings 7 are wound inthe state in which the stator core 1 is developed approximatelylinearly. When the wires are thin, the stator core 1 may be developedlinearly as described above. However, when the wires are thick, thestator core 1 may be developed more than a linear state so that the poleportions 4 are disposed externally radially.

Further, while the spigot portions 6 are formed around the entirecircumference of the winding frames 5 in the first embodiment, they maybe of course formed around only the portions where the winding frames 5exist. When the spigot portions 6 are formed around the entirecircumference of the winding frames 5, they can be reliably fitted tothe not shown brackets, whereas when the spigot portions 6 are formedonly around the portions where the winding frames 5 exist, the statorcore 1 can be manufactured easily.

Second Embodiment

FIG. 7 is an overall perspective view showing the stator for thestarter-motor of a second embodiment of the invention; and FIG. 8 is aperspective view showing a manufacturing process of the stator of thesecond embodiment. In the second embodiment, no spigot portion is formedon winding frames 5 which are formed around pole portions 4 by the resinmolding method.

In the second embodiment, a second cylindrical yoke 8 whose axial lengthis shorter than that of a stacked core 1 is combined with the outercircumference of the stacked core 1 as shown well in FIG. 8. Then, thestepped portions formed by the stacked core 1 and the second cylindricalyoke 8 act as spigot portions 6 to be combined with not shown brackets.

In the stator for the starter motor of the second embodiment arranged asdescribed above, the second cylindrical yoke 8 is disposed around theouter circumference of the stacked core 1. As a result, a change in theradial direction of the second cylindrical yoke 8 can change thethickness of the overall yoke without replacing a metal mold, whichpermits optimum thicknesses applicable to many types of stacked cores tobe obtained.

Further, the axial length of the second cylindrical yoke 8 is shorterthan that of the stacked core 1 so as to form the spigot portions 6 tobe fitted to the brackets, which can reduce the manufacturing cost ofthe stacked core 1 because the machining necessary to form theconventional spigot portions 6 is not necessary.

Note that the second cylindrical yoke 8 is made by a clinch formingmethod so as to be provided with clinch portions 9. It may be possibleto clinch the second cylindrical yoke 8 so that the inside diameterthereof is made smaller than the outside diameter of the stacked core 1and to secure the second cylindrical yoke 8 to the stacked core 1 makinguse of spring back.

Third Embodiment

FIG. 9 is an overall perspective view showing the stator for the startermotor of a third embodiment of the invention. In the third embodiment,no spigot portion is formed on winding frames 5 which are formed aroundpole portions 4 by means of the resin molding method similarly to thesecond embodiment.

Then, in the third embodiment, a second cylindrical yoke 18 whose axiallength is longer than that of a stacked core 1 is combined with theouter circumference of the stacked core 1 as shown in FIG. 9. Then, thestepped portions formed by the stacked core 1 and the second yoke 18 actas spigot portions 6 to be combined with not shown blackets.

In the stator for the starter motor of the third embodiment arranged asdescribed above, the axial length of the second yoke 18 is longer thanthat of the stacked core 1 to thereby form the spigot portions 6 to befitted to the not shown brackets, which can reduce the manufacturingcost of the stacked core 1 because the machining necessary to form theconventional spigot portions 6 is not necessary.

Fourth Embodiment

FIG. 10 is an overall perspective view showing the stator for thestarter motor of a forth embodiment of the invention. In the fourthembodiment, no spigot portion is formed on winding frames 5 which areformed around pole portions 4 by means of the resin molding methodsimilarly to the embodiment 2.

Then, in the fourth embodiment, stepped portions are formed on the outercircumference of a stacked core 1 at the ends in the axial directionthereof as shown in FIG. 10 so as to form spigot portions 6 to be fittedto brackets. The height of the stepped portions can be adjusted bydisposing a predetermined number of thin sheet members each having asmaller outside diameter as necessary. That is, the stepped portions areformed around the outer circumference using two types of the stackedcores having a different outside diameter.

Note that the stepped portions acting as the spigot portions 6 may beformed by machining a stacked core 1 which entirely has a given outsidediameter up to the ends thereof by, for example, a lathe or the like.

Fifth Embodiment

FIG. 11 is an overall perspective view showing the stator for thestarter motor of a fifth embodiment of the invention; FIG. 12 is aperspective view showing a manufacturing process of the stator of thefifth embodiment; and FIG. 13 is a sectional view of the starter motorof the fifth embodiment. In the fifth embodiment, no spigot portion isformed on winding frames 5 which are formed around pole portions 4 by aresin molding method similarly to the second embodiment.

Then, in the fifth embodiment, ring-shaped members 10 each having astepped portion whose cross section is formed in a crank-shape, arefitted around the stacked core 1 at both the ends in the axial directionthereof, and the stepped portions of the ring-shaped members 10 are usedas spigot portions 6 which are to be combined with two brackets 11coupled with both the ends of the stacked core 1.

The ring-shaped members 10 are made of stamped steel sheets or the like.Each ring-shaped member 10 is fixed at a predetermined position by beingheld between each bracket 11 and the stacked core 1 by through bolts 12.As a result, it is not necessary to previously joint the ring-shapedmembers 10 to the stacked core 1.

In the stator, which is composed of the stacked core, for the startermotor, the stacked core being arranged such that a plurality of sheetmembers each having the yoke portion and the pole portion are disposedlike a band, adjacent sheet members are stacked and coupled with eachother so that the ends of the yoke portions thereof are overlapped, theplurality of sheet members are made to the annular shape by being bentat the coupled portions thereof to cause the pole portions to face thecenter of the annular shape, and the plurality of sheet members areformed in at least an approximately linear shape when developed, theresin winding cores are interposed between the pole potions and thewires wound around the pole portions. The provision of the resin windingframes permits the field windings to be directly wound around the poleportions. The direct contact of the field windings with the poleportions is prevented by the winding frames, which improves theinsulating property of the wound wires without damaging the insulatingfilms thereof. Further, the use of the stacked core eliminates the needof a large processing apparatuses, and the stator core can be made bysimple apparatuses such as a multi-purpose press, molding machine,winder and the like, which reduces the manufacturing cost of the statorcore.

Further, the spigot portion, which are fitted to the brackets, areformed at the ends of the winding frame in the axial direction thereof.The formation of the spigot portions on the winding frames permit thespigot portions to be formed easily, by which the manufacturing cost ofthe stator core can be reduced.

Further, the winding frames are made by the resin molding method, andthe spigot portions are made simultaneously with the winding frames madeby the resin molding method, which makes it unnecessary to performconventional machining and can reduce the manufacturing cost of thestator core.

Further, the second cylindrical yoke is disposed around the outercircumference of the stacked core. As a result, a change of the radialthickness of the second yoke can change the overall thickness of theyoke without replacing the metal mold of the stacked core. Thus, optimumthicknesses applicable to many types of stacked cores can be obtainedand the wasteful use of materials can be eliminated.

Further, the axial length of the second yoke is shorter than that of thestacked core so as to form the spigot portions to be fitted to thebrackets. As a result, the machining necessary to make the conventionalspigot portions is made unnecessary, whereby the manufacturing cost ofthe stator core can be reduced.

Further, the axial length of the second yoke is longer than that of thestator core so as to form the spigot portions which are fitted to thebrackets. As a result, conventional machining necessary to make thespigot portions is made unnecessary, whereby the manufacturing cost ofthe stator core can be reduced.

Further, the second yoke is made by the clinch manufacturing method. Asa result, the second cylindrical yoke can be easily secured to thestacked core by clinching the second yoke so that the inside diameterthereof is made smaller than the outside diameter of the stator core andsecuring it on the stacked core making use of the spring back.

Further, the stepped portions are formed around the outer circumferenceof stacked core at the ends in the axial direction thereof so as to formthe spigot portions to be fitted to the brackets. As a result, themachining necessary to make the conventional spigot portions is madeunnecessary, whereby the manufacturing cost of the stator core can bereduced.

Further, the stepped portions are formed by overlapping the two types ofthe stacked cores having a different outside diameter. As a result, themachining necessary to make the conventional spigot portions is madeunnecessary, whereby the manufacturing cost of the stator core an bereduced. Further, the height of the stepped portions can be adjusted byappropriately changing the number of stacked core sheets.

In addition, the stepped portions are formed by machining the ends ofthe circumference of the stacked core. As a result, the machining of thespigot portions can be performed more easily than the machining carriedout to make conventional spigot portions, whereby the manufacturing costof the stator core can be reduced.

Further, the ring-shaped members each having the stepped portion aredisposed at the ends of the stacked core in the axial direction thereof.The provision of the ringshaped member formed of the thin sheet membercan make the outside diameter of the brackets smaller as compared with acase in which the spigot portions are made by machining.

What is claimed is:
 1. A stator, which is comprised of a stacked core,for a starter motor, said stacked core comprising a plurality of sheetmembers comprising two groups of sheet members, wherein each of thesheet members of a first group comprise a yoke portion and a poleportions the pole portion extending from the yoke portion, and whereineach of the sheet members of a second group consists essentially of anarc-shaped yoke portion, and further wherein the first group and secondgroup of sheet members are alternately arranged so as to be capable ofbeing disposed as a band, adjacent sheet members are stacked and coupledwith each other so that the ends of the yoke portions thereof areoverlapped, said plurality of sheet members are made to an annular shapeby being bent at the coupled portions thereof to cause said poleportions to face the center of said annular shape, and said plurality ofsheet members are capable of being formed in at least an approximatelylinear shape thereby facilitating access to the pole pieces duringattachment of wires.
 2. A stator, which is comprised of a stacked core,for a starter motor said stacked core being arranged such-that aplurality of sheet members each having a yoke portion and a pole portionare capable of being disposed as a band, adjacent sheet members arestacked and coupled with each other so that the ends of the yokeportions thereof are overlapped, said plurality of sheet members aremade to an annular shape by being bent at the coupled portions thereofto cause said pole portions to face the center of said annular shape,and said plurality of sheet members are capable of being formed in atleast an approximately linear shape thereby facilitating access to thepole pieces during attachment of wires, wherein resin winding frames areinterposed between said pole portions and wires wound around said poleportions, wherein spigot portions, which are capable of fitting tobrackets, are formed at ends of said winding frames in the axialdirection thereof.
 3. A stator for a starter motor according to claim 1,further comprising resin winding frames interposed between said poleportions and wires wound around said pole portions, wherein said windingframes are molded resin.
 4. A stator for a starter motor according toclaim 1, wherein a second cylindrical yoke is disposed around the outercircumference of said stacked core.
 5. A stator for a starter motor,which is comprised of a stacked core, said stacked core being arrangedsuch that a plurality of sheet members each having a yoke portion and apole portion are capable of being disposed as a band, adjacent sheetmembers are stacked and coupled with each other so that the ends of theyoke portions thereof are overlapped, said plurality of sheet membersare made to an annular shape by being bent at the coupled portionsthereof to cause said pole portions to face the center of said annularshape, and said plurality of sheet members are capable of being formedin at least an approximately linear shape thereby facilitating access tothe pole pieces during attachment of wires, wherein resin winding framesare interposed between said pole portions and wires wound around saidpole portions, wherein a second cylindrical yoke is disposed around theouter circumference of said stacked core, and further wherein the axiallength of said second yoke is shorter than that of said stacked core soas to form spigot portions capable of fitting to brackets.
 6. A statorfor a starter motor, which is comprised of a stacked core, said stackedcore being arranged such that a plurality of sheet members each having ayoke portion and a pole portion are capable of being disposed as a band,adjacent sheet members are stacked and coupled with each other so thatthe ends of the yoke portions thereof are overlapped, said plurality ofsheet members are made to an annular shape by being bent at the coupledportions thereof to cause said pole portions to face the center of saidannular shape, and said plurality of sheet members are capable of beingformed in at least an approximately linear shape thereby facilitatingaccess to the pole pieces during attachment of wires, wherein resinwinding frames are interposed between said pole portions and wires woundaround said pole portions, wherein a second cylindrical yoke is disposedaround the outer circumference of said stacked core, and further whereinthe axial length of said second yoke is longer than that of said stackedcore so as to form spigot portions capable of fitting to brackets.
 7. Astator for a starter motor, which is comprised of a stacked core, saidstacked core being arranged such that a plurality of sheet members eachhaving a yoke portion and a pole portion are capable of being disposedas a band, adjacent sheet members are stacked and coupled with eachother so that the ends of the yoke portions thereof are overlapped, saidplurality of sheet members are made to an annular shape by being bent atthe coupled portions thereof to cause said pole portions to face thecenter of said annular shape, and said plurality of sheet members arecapable of being formed in at least an approximately linear shapethereby facilitating access to the pole pieces during attachment ofwires, wherein resin winding frames are interposed between said poleportions and wires wound around said pole portions, wherein a secondcylindrical yoke is disposed around the outer circumference of saidstacked core, and further wherein said second yoke further comprises aclinch portion.
 8. A stator for a starter motor, which is comprised of astacked core, said stacked core being arranged such that a plurality ofsheet members each having a yoke portion and a pole portion are capableof being disposed as a band, adjacent sheet members are stacked andcoupled with each other so that the ends of the yoke portions thereofare overlapped, said plurality of sheet members are made to an annularshape by being bent at the coupled portions thereof to cause said poleportions to face the center of said annular shape, and said plurality ofsheet members are capable of being formed in at least an approximatelylinear shape thereby facilitating access to the pole pieces duringattachment of wires, wherein resin winding frames are interposed betweensaid pole portions and wires wound around said pole portions, whereinstepped portions are formed around the outer circumference of saidstacked core at the ends in the axial direction thereof so as to act asspigot portions capable of fitting to brackets.
 9. A stator for astarter motor according to claim 8, wherein said stepped portions areformed by overlapping two types of said stacked cores having a differentdiameter.
 10. A stator for a starter motor according to claim 8, whereinsaid stepped portions are formed by machining the outer circumference ofsaid stacked core.
 11. A stator for a starter motor, which is comprisedof a stacked core, said stacked core being arranged such that aplurality of sheet members each having a yoke portion and a pole portionare capable of being disposed as a band, adjacent sheet members arestacked and coupled with each other so that the ends of the yokeportions thereof are overlapped, said plurality of sheet members aremade to an annular shape by being bent at the coupled portions thereofto cause said pole portions to face the center of said annular shape,and said plurality of sheet members are capable of being formed in atleast an approximately linear shape thereby facilitating access to thepole pieces during attachment of wires, wherein resin winding frames areinterposed between said pole portions and wires wound around said poleportions, wherein ring-shaped members having stepped portions aredisposed at the ends of said stacked core in the axial directionthereof.